1. Field of the Invention
The present invention relates generally to a centrifugal fan, and more particularly to a centrifugal fan having thinner thickness and higher performance. Also, the noise made by the centrifugal fan is lowered.
2. Description of the Related Art
Recently, various electronic apparatuses (such as notebooks or tablets) have become thinner and thinner and lighter and lighter. As a result, the internal space of the electronic apparatus is quite limited. In this case, the cooling fan mounted in the internal space is required to have a thin thickness. Also, the space between the cooling fan and adjacent components is quite limited so that the heat dissipation effect of the cooling fan is poor. Especially, under the limitation of space, the airflow of the cooling fan can be hardly uniformly sent out from the outlet of the cooling fan. This will affect the heat dissipation efficiency.
A prior centrifugal fan is disclosed. Multiple blades are disposed on a top face of the hub of the centrifugal fan. The second ends of the blades are annularly arranged to together define a virtual geometrical configuration. The virtual geometrical configuration has a maximum outer diameter. The second ends of each two adjacent blades are spaced by a gap. The gap is smaller than the maximum outer diameter of the virtual geometrical configuration so as to enhance the heat dissipation effect.
The above centrifugal fan has better heat dissipation effect. However, there is still a problem existing in such centrifugal fan. That is, the blades are disposed on the top face of the hub. Therefore, the axial height of such centrifugal fan is higher than that of the hub of the common centrifugal fan. In other words, the original height of the hub plus the height of the blades will lead to a considerable increase of the total axial height of the fan impeller. As a result, the total height of the fan frame for receiving the fan impeller is greatly increased. As shown in FIG. 2, the total axial height of the fan frame is the axial height of the sidewall section plus the axial height of the lateral outlet or inlet. The axial height of the fan frame equals the total height of the fan impeller. In this case, the conventional centrifugal fan can be hardly thinned and the thickness cannot be saved. Under such circumstance, it will be impossible to install the centrifugal fan in the limited internal space of the electronic apparatus. Therefore, it has become a critical issue in this field how to thin the centrifugal fan, while still having an excellent heat dissipation performance.